alvherre@alvh.no-ip.org (Alvaro Herrera) writes:
> Chris Browne wrote:
>
>> It strikes me as a slick idea for autovacuum to take on that
>> behaviour. If the daily backup runs for 2h, then it is quite futile
>> to bother vacuuming a table multiple times during that 2h period when
>> none of the tuples obsoleted during the 2h period will be able to be
>> cleaned out until the end.
>
> Hmm, yeah, sounds useful. There's one implementation issue to notice
> however, and it's that the autovacuum process dies and restarts for each
> iteration, so there's no way for it to remember previous state unless
> it's saved somewhere permanent, as the stats info is.
Hmm. It restarts repeatedly??? Hmmm...
> However this seems at least slightly redundant with the "maintenance
> window" feature -- you could set a high barrier to vacuum during the
> daily backup period instead. (Anybody up for doing this job?)
In effect, this would be an alternative to the "window" feature. You
open the window by starting pg_dump; pg_autovacuum would automatically
notice that as the eldest XID, and stop work until the pg_dump
actually finished.
In a way, it strikes me as more elegant; it would automatically notice
"backup windows," noticing *exact* start and end times...
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